[0001] The present invention relates to stabilizing insoluble olefinic polymers in bitumen
by an in-situ reaction.
[0002] It often is necessary to maintain insoluble solid phase particulates or immiscible
liquid phase droplets in suspension in a continuous liquid phase for a variety of
purposes and emulsifiers of various type have been used to achieve such results. One
common application is the emulsification of non-polar liquid hydrocarbons in water,
in which the individual liquid hydrocarbon droplets remain discrete due to electrostatic
repulsion of the adsorbed emulsifiers at the droplet interface.
[0003] In non-aqueous emulsions, there are no electrostatic forces and hence alternative
methods must be employed to prevent coalescence and separation of the dispersed phase.
One specific problem area in the latter category is the provision of stabilized bitumen-polymer
compositions for use as a road surface asphalt and related uses.
[0004] It is well known that certain characteristics of bitumens can be improved by modification
by or addition of polymeric materials. For example, EP-A-317,025 to Shell Internationale
Research Maatschappij BV, discloses a bitumen composition useful in road paving applications
containing an asymmetric radial block copolymer which exhibits increased toughness
and tenacity. Recently published PCT Publication No. WO 90/02776, to Société Nationale
Elf Aquitaine discloses bitumens modified with a copolymer of styrene and a conjugated
diene and a coupling agent, such as sulfur.
[0005] Among the properties of the bitumen composition which potentially can be improved
by dispersion of polymeric materials therein, particularly in roadway applications,
are increased rutting resistance, enhanced low temperature cracking resistance, improved
traction, better adhesion/cohesion, elevated tensile strength as well as other benefits.
However, a problem often encountered with bitumen-polymer mixtures is an incompatibility
of the bitumen and polymer components. Bitumens and most polymers, especially polyolefins
such as polyethylene, are not readily miscible with each other in a molten state.
A tendency exists for a dispersed molten polymer to agglomerate and coalesce rapidly
and not remain dispersed when stirring of the bitumen composition ceases. Once such
phase separation occurs, the potential for the improved properties is lost.
[0006] One approach to overcoming this problem has been the use of another additive to form
a stabilized bitumen gel as described in, for example, United States Patent No. 4,018,730
(issued April 19, 1977 to McDonald). This approach has the disadvantage of providing
a thickened or jellied material, the higher viscosity of which has less desirable
working characteristics than is desirable for conventional uses of bitumens.
[0007] More closely related to bituminous compositions obtainable with the present invention
are those disclosed in, for example, United States Patent No. 4,314,921 (issued February
9, 1982 and assigned to Novophalt SA) and German Offenlegungsschrift 39 20 878 (published
January 4, 1990 and assigned to Novophalt SA). These documents disclose specific methods
of physical mixture to achieve homogenization of molten bitumens and thermoplastic
polymers, such as polyethylene. Such specialized mixing methods have heretofore been
found to be necessary because of the difficulty of obtaining adequate dispersion of
polymer components in the bituminous phase to provide desired qualities in the working
material produced. As described in United States Patent No. 4,314,921, shearing forces
which degrade the polymer are apparently necessary to achieve homogenization. Further,
there is a tendency for the homogenized bitumens and polymers to undergo gross phase
separation even after such homogenization, necessitating continuous stirring and local
or on-site preparation. Commercial applications of the Novophalt process as described
in this patent thus include the addition of paving components,. such as sand and gravel,
to the homogenized mixture within a relatively short period of time after the homogenization
process is complete.
[0008] United States Patent No. 4,154,710 of Maldonado et al. (issued May 15, 1979 to Elf
Union) discloses a bitumen modified by heating bitumen in the presence of polyisobutene
or a mixture of fatty acid esters (i.e. esters of oleic acid, palmitic acid, stearic
acid with high alcohols, such as lanosterol, cholesterol or isocholesterol) consisting
of a natural extract of mutton suet, in the presence of sulphur. Apparently stable
mixtures were obtained with the admixture of polymers, such as isobutene-butadiene
copolymer, ethylene-cylcopentadiene copolymer and polybutene-polyisobutene copolymers.
[0009] In U.S. Patent No. 4,978,698, assigned to the assignee hereof and naming Raymond
T. Woodhams as inventor, there is described another approach to stabilizing the dispersed
polymer phase. As described therein, an emulsifier system for providing a dispersed
polyethylene phase comprises a polyethylene wax having a molecular weight of about
1000 to about 10,000 and terminally functionalized with acidic groups, particularly
carboxylic acid groups. Inorganic metal oxides may be provided in chemical association
with the acidic groups of the polyethylene wax. While these compositions exhibit a
degree of stability, phase separation often is observed to occur.
[0010] Other attempts to maintain a polymeric material dispersed in bitumen have involved
the use of dispersing agents to improve compatibility between polymer and asphalt
to resist coalescence and phase separation. However, none of these approaches has
found success as a viable commercial operation. For example, some of the polymeric
modifiers used as dispersing agents tend to precipitate on pavement rolling equipment,
causing severe paving problems.
[0011] This prior art does not contemplate systems which maintain insoluble or incompatible
polymer particles or droplets stabilized in liquid asphalt medium by steric stabilization
and which are resistant to phase separation at elevated temperatures for long periods
of time under quiescent conditions, as in the present invention.
[0012] We now have surprisingly found that we are able to achieve stable dispersions of
insoluble polymers in bitumens which exhibit stability against phase separation in
the liquid medium, in contrast to the prior art. Such stability is achieved by employing
a novel in-situ stabilization procedure, as described below, which results in a steric
stabilization of the insoluble polymer particles as a dispersed phase in the bitumen.
[0013] Accordingly, in one aspect of the present invention, there is provided a stable bitumen
composition, comprising:
a continuous bitumen phase;
a particulate phase of an insoluble olefinic polymer dispersed in said bitumen phase;
and
a steric stabilizer of (a) a first component comprising a polydiene, soluble in said
bitumen, and (b) a second component comprising an olefinic polymer, the same as or
different from the olefinic polymer of the particulate phase, miscible with said particulate
phase so as to be anchored thereto, and chemically bonded to said first component
to maintain dispersed particles of said particulate phase spaced from each other in
said bitumen phase, so as to inhibit separation of said particulate phase from said
bitumen phase by progressive coalescence of the dispersed particles.
[0014] The particulate phase may be in the form of solid particles or liquid droplets. The
steric stabilizer component of the composition is formed by in-situ formation of chemical
bonding among the steric stabilizer forming components and anchoring to the particulate
organic material to form a specific steric layer having a partially crosslinked structure
of chemical bonds binding the liquid phase and particulate phase in spaced relation.
[0015] Thus, the invention also provides a method of forming a stable bitumen composition,
comprising:
(a) forming, in a continuous bitumen phase, a particulate phase of an insoluble olefinic
polymer dispersed in said bitumen phase by dispersing the olefinic polymer in the
bitumen phase, at an elevated temperature above the fusion temperature of the olefinic
polymer, in the presence of a first component comprising a functionalized polydiene
soluble in said bitumen and a second component comprising a functionalized olefinic
polymer, the same as or different from the olefinic polymer of the particulate phase
and miscible with the particulate phase for anchoring thereto; and
(b) effecting chemical bonding between the first and second components by interaction
of the functional groups therein to form a steric stabilizer anchored to the particulate
phase and soluble in the bitumen phase, to maintain dispersed particles of said particulate
phase spaced from each other in said bitumen phase, so as to inhibit separation of
said particulate phase from said bitumen phase by progressive coalescence of the dispersed
particles.
[0016] For a better understanding of the invention, and to show how the same may be carried
into effect, reference will now be made, by way of example, to the accompanying drawings,
in which:-
Figure 1 is a high magnification (x 1650) photograph of a sample of a bitumen-polyethylene
composition prepared according to the method of Example 1 described below and not
in accordance with the invention, showing the presence of coalesced polyethylene particles
in the bitumen as they appear after holding for 3 hours at 160°C without stirring;
Figure 2 is a high magnification (x 1650) photograph of a sample polyethylene-bitumen
composition stabilized against gross phase separation as obtained using the method
of Example 3 according to the invention, after 3 days at 160°C without stirring; and
Figure 3 is a high magnification (x 1650) photograph of a stable polyethylene-bitumen
dispersion as obtained using the method of Example 3 according to the invention, after
repeated reheating of the sample from room temperature to 160°C, three times without
stirring.
[0017] The present invention is directed to the stabilization of insoluble olefinic polymer
particles in a continuous bitumen phase by the formation
in-situ of chemical bonding and cross-linking between the continuous bitumen phase and the
insoluble olefinic polymer particles.
[0018] A major application of the principles of the present invention is in the provision
of stabilized polymer-modified bitumen compositions suitable for use as a paving material
for all paving applications, including hot mix, cut-backs, emulsions and crack fillers,
as well as other uses. The term "bitumen" used herein means a class of black or dark-colored
(solid, semi-solid or viscous) cementitious substances, natural or manufactured, composed
principally of high molecular weight hydrocarbons of which asphalts, tars, pitches
and asphalites are typical. The term "asphalt" used herein means a dark, brown to
black, cementitious material, solid or semi-solid in consistency, in which the predominating
constituents are bitumens that occur in nature, as such, or are obtained as residue
in petroleum refining.
[0019] The bitumen comprises the major continuous phase of the polymer-modified bitumen
compositions and the polymer is dispersed in the bitumen, either as solid particles
or liquid droplets, depending on the nature of the polymer and the temperature of
the composition.
[0020] The polymer component of the bitumen composition may be any olefinic polymer which
can be melted or particulated for dispersion in the bitumen and which imparts useful
properties thereto. Generally, such polymer component comprises homopolymers and copolymers
of ethylene and propylene, particularly homopolymers and copolymers of ethylene. However,
other polymeric materials, such as crumb rubber, may be employed.
[0021] Virtually any grade of polyethylene polymer or copolymer may be used to provide the
polymer component of the bitumen composition. One advantage provided by the present
invention as it is applied to bitumen-polyolefin and other such compositions, is the
ability to employ comingled, recycled or waste polyolefins in providing the dispersed
polyolefin phase, rather than requiring virgin material.
[0022] For the purpose of formation of the stable emulsion herein, bitumen is heated to
a temperature above the fusion temperature of the polyethylene or other olefinic polymer,
which then is dispersed in the bitumen by high shear mixing to form a uniform dispersed
phase of liquid droplets in the bitumen, which, in the presence of the steric stabilizer,
remain dispersed, when the high shear mixing ceases. However, any other convenient
procedure for effecting dispersion of the particulate polymer phase may be employed.
The quantity of polyethylene or other polymer dispersed in the bitumen may vary widely,
depending on the properties desired and the end use to which the composition is to
be put. Generally, for road pavement, the quantity of polymeric material present in
the composition varies from 0.1 to 20 wt% of the bitumen, preferably 0.5 to 10 wt%
of the bitumen, and most preferably 2.5 to 7 wt% of the bitumen.
[0023] While the bitumen is hot and the liquid droplets of polyethylene are uniformly dispersed
by the shear forces applied thereto, the emulsion is stabilized in-situ by the chemical
reactions described in more detail below. When such reactions are complete and the
shear forces are removed, the polyethylene-modified bitumen composition shows no tendency
to phase separate at elevated temperatures in the range of about 100° to 200°C and
remains stable in the absence of stirring. A photograph of a sample of composition
provided in accordance with the invention is seen in Figure 2, from which the dispersed
nature of the small polyethylene droplets can be seen. This situation is to be contrasted
with the photograph of Figure 1, which depicts the situation only a few hours after
removal of stirring from a composition formed by high shear mixing but not stabilized
in accordance with the present invention.
[0024] An additional benefit which is achieved by the steric stabilization of the polyethylene
or other olefin polymer achieved herein is that small discrete particles of polyethylene
are spontaneously created by dispersion of the molten polymer, with a particle size
which can be adjustable to obtain different average particle sizes as required, and
may be less than one micron, which is an important attribute to toughness of a pavement
or other end use of the composition. It is noted that simple mixing does not achieve
such small dimensions, even when high shear conditions are employed, unless some dispersing
agents are employed, for example, to lower interfacial tension and differences in
viscosity between dispersed phase and continuous phase.
[0025] The composition also may be cooled to ambient temperature, may be reheated up to
about 160°C or more up to about 200°C several times and may be maintained at such
high temperature for several days, without any tendency to phase separation. A photograph
of a sample of composition which has been heated up three times to 160°C from room
temperature is seen in Figure 3. As can be seen, the small polyethylene droplets remain
dispersed. This attribute is important, since on-site formation of the polyethylene-modified
bitumen composition is not required, in contrast to the situation which exists with
high-sheared non-stabilized compositions. The emulsion is inherently stable by reason
of the chemical bonding and hence may be solidified and reheated without loss of uniformity
or stability.
[0026] The composition of the invention may be formulated for use in a number of ways. As
discussed below, a stabilized concentrate may be formed with which bitumen and polyethylene
is mixed on site. Alternatively, a composition may be provided containing the bitumen
and stabilizer components which is shipped to the site of use and to which the polyethylene
is added at the site. In addition, all components may be mixed at the same location
to form the composition.
[0027] For the purpose of achieving stabilization of dispersed polyethylene or other polymer
in bitumen, it is necessary to achieve reaction of a number of components with each
other and association with the continuous and dispersed phases.
[0028] Stabilization is achieved using a plurality of components. A first component is a
bitumen-soluble component comprising a polydiene which may have a bitumen-soluble
first portion, generally bitumen itself, partially covalently-bonded thereto.
[0029] The polydiene may be a conjugated diene polymer or polydiene-based copolymer. Preferably,
it is a polydiene rubber having a molecular weight in the range of from 500 to 60,000,
more particularly, a polydiene rubber having a molecular weight in the range cf from
1,000 to 12,000. Covalent linkage of the polydiene to the bitumen may be effected
by some reactive agents, which can generate free radicals, such as peroxide or elemental
sulphur with or without an accelerator and a sulphur donor.
[0030] A second component is an olefinic polymer which is miscible with the dispersed particulate
phase so as to be anchored thereto in the stable dispersion and which also is capable
of covalent bonding, such as by nucleophilic linkage, with the polydiene of the first
component. Nucleophilic linkage is derived from the reaction of a functional group
having a nucleophilic heteroatom, such as O, N or S, with an electrophilic atom, such
as a carbonyl carbon in an anhydride group.
[0031] The second component preferably has a similar backbone structure to the olefinic
polymer of the particulate phase, usually polyethylene or other polyolefin, which
permits the polymer chain of the second component to blend with the molten dispersed
polymer particles and to become anchored thereto. The second component may have a
molecular weight of 10,000 to 1,000,000, preferably from 50,000 to 500,000.
[0032] Covalent linkage of the functionalized olefinic polymer of the first component to
the bitumen-compatible polydiene of the second component is effected, usually by reaction
between a nucleophilic group, such as an amino group or carboxyl group, for example,
provided on the polydiene, and an electrophilic group, such as a carbonyl group, for
example, present in an anhydride group, on the olefinic polymer.
[0033] In one particular embodiment of the invention, there may be employed as the first
component, a polybutadiene or polybutadiene-based copolymer partially functionalized
with a nucleophilic amino group,and as the second component there may be employed
a functionalized polyethylene, such as carboxylated polyethylene.
[0034] Other known nucleophiles include hydroxyl, carboxyl and sulphydryl and other known
electrophiles include anhydrides and other carbonyl-containing groups, and epoxy and
isocyanate groups. The amine-terminated poly(butadiene-co-acrylonitrile) of the examples
is a readily-available commercial product used for exemplification of the principles
herein. Other amine functionalized polydiene polymers and butadiene copolymers containing
substantially polybutadiene component with e.g., styrene comonomer, are just as or
more suitable and effective. Further, a polydiene polymer of higher molecular weight
may be more desirable as long as it is soluble or compatible at the operating temperature.
[0035] Other well known covalent linkages may be employed herein to bond first and second
components. Such covalent linkage may be achieved by other means, for example, a carboxylated
polydiene and a carboxylated polyethylene may be linked by a difunctional aminol,
diamine or diol.
[0036] In addition to these components, a liquid polybutadiene, soluble in or compatible
with the bitumen, may be provided as a third component of the stabilizer. In some
cases, the polybutadiene or other polydiene may be omitted and the combination of
the functionalized polydiene and the functionalized polymer is sufficient to effect
the necessary reactions to achieve steric stabilization. If included, it is necessary
that the butadiene or other chain-extendable diene or polymer be of a molecular weight
such that the butadiene is soluble in or compatible with the bitumen, so as to facilitate
the cross-linking with the other components of the stabilizer and chain extension
of the butadiene upon free-radical coupling. The molecular weight (Mw) range of this
third component may be from a low molecular weight, such as from 500 to 45,000 or
higher, as long as the polybutadiene or its copolymer is soluble in or compatible
with the bitumen at the mixing temperature, generally from 150° to 200°C.
[0037] The components of the stabilizer composition, after addition to the stirred elevated
temperature mixture of polyethylene and bitumen, are subjected to free-radical reaction,
using a free-radical initiator, such as sulphur Usually, however, it is more practical,
because of viscosity considerations, to form a pro-stabilizer from the stabilizer
composition components which has pendant polymeric chains. Upon subsequent dispersion
of the polymer in the bitumen as liquid droplets at elevated temperature, the liquid
polymer droplets absorb the pendant polymeric chains and the stabilizer composition
thereby becomes anchored to the polymer particles, providing the gel envelope described
below.
[0038] The functionalized polydiene rubber and functionalized polyethylene or its copolymer
react to effect covalent bonding one to the other. Upon initiation of the free radical
reaction between the various polydiene components as well as reactive components of
the bitumen phase, such as by sulphur the polybutadiene undergoes a series of cross-linking
reactions to form a gel envelope which contributes significantly to the stability
of the dispersed polymer particles.
[0039] In this regard, the free radical reaction causes cross-linking of the polybutadiene,
cross-linking of the polybutadiene to the functionalized butadiene and linking to
the bitumen. The net effect of these various reactions is to form an extended polybutadiene-based
network with a partially cross-linked structure anchored to each of the polymer particles
and swollen by the bitumen phase, to provide a gel envelope about the polymer particles,
which prevents coalescence of the polymer particles.
[0040] The various components of the steric stabilizer are chemically-interlinked with each
other and anchored to the polymer particles and the polybutadiene-based layer with
a cross-linked structure, which is swollen by the bitumen medium)ensures a substantially
fixed relationship of the polymer particles one to another within the continuous bitumen
phase. The polybutadiene-based layer also is bonded to bitumen. The particles are
prevented from approaching each other and coalescing, if molten, by the gel lattice
of linked polymeric chains formed around each particle which provides a steric envelope
about the individual particles. The particles, when in solid form, resist flocculation
or precipitation for the same reason.
[0041] The compositions of the present invention may be produced in any convenient manner.
In one embodiment, carboxylated polyethylene, liquid polybutadiene (as required),
amino-terminated poly(butadiene-co-acrylonitrile) and elemental sulphur may be dispersed
in bitumen. For a conventional hot mix asphalt paving application, a preferred ratio
of carboxylated polyethylene to bitumen is from 0.1 to 5 per cent by weight, more
preferably, from about 0.3 to about 1 per cent by weight, and a preferred ratio of
aminofunctionalized butadiene based copolymer is from 0.1 wt% to 3 wt%, more preferably
from 0.2 to about 1 wt%. The amount of liquid butadiene may be preferably in the range
of from 0.1 to about 10 wt%, more preferably from 0.4 to 6 wt%, of bitumen. The amount
of sulphur is preferably 0.1 per cent and 10 per cent of the total mixture, by weight,
preferably from 0.2 to 5 wt%. For other applications, for example, roofing, the relative
proportions of components may vary.
[0042] The four ingredients of this embodiment are added to a heated bitumen with stirring,
which may comprise high shear mixing conditions at about 100° to about 250°C, preferably
about 130° to about 200°C for a suitable period of time, which may be 0.1 to 3.5 hours,
usually 0.25 to 1 hour, to form a homogeneous composition, which can be termed a concentrate.
The use of vacuum or inert gases may be beneficial in certain instances. This concentrate
constitutes one aspect of the present invention and may be shipped to the site of
formation of the final blend from concentrate, additional bitumen and polyethylene.
[0043] Accordingly, in this aspect of the invention, there is provided a stable bitumen
composition, comprising:
a continuous bitumen phase;
a particulate phase of an insoluble olefinic polymer dispersed in said bitumen phase;
and
a steric stabilizer of (a) a first component comprising a polydiene, soluble in said
bitumen, and (b) a second component comprising an olefinic polymer, the same as or
different from the olefinic polymer of the particulate phase, miscible with said particulate
phase so as to be anchored thereto, and chemically bonded to said first component
to maintain dispersed particles of said particulate phase spaced from each other in
said bitumen phase, so as to inhibit separation of said particulate phase from said
bitumen phase by progressive coalescence of the dispersed particles.
[0044] There is also provided a method of forming a bitumen composition, comprising:
dissolving a functionalized polydiene in bitumen; dispersing a functionalized olefinic
polymer in the bitumen; and
reacting the functionalized olefinic polymer and the functionalized polydiene so as
to bind the olefinic polymer to the polydiene, thereby to form in the bitumen a pro-steric
stabilizer for, in use, maintaining a dispersed particulate phase of an olefinic polymer,
the same as or different from the olefinic polymer of the pro-steric stabiliser, to
be added to the composition.
[0045] The olefinic polymer, preferably polyethylene, requiring dispersion in the bitumen
is added to the concentrate at the elevated temperature, along with additional bitumen,
if and as required, and stirring is continued until the polyethylene is dispersed
into the system to form a stable polymer-asphalt composition. Pendant olefinic polymer
chains on the pro-steric stabilizer are absorbed by the molten polyethylene and thereby
blend therein, so that the stabilizer material becomes anchored to the polyethylene
particles. The amount of polyethylene is present in such composition is preferably
between 0.1 to 20 percent by weight, and more preferably from 1 to 5 percent by weight,
for a conventional hot mix asphalt paving application. Greater or less amounts of
polyethylene or other dispersed polymer may be employed depending on the end use of
the composition.
[0046] The present invention thus provides a stabilized molten bituminous mixture having
polyethylene particles which do not coalesce at elevated temperatures. The inventors
have thus found that, while a stabilizer having a polyethylene portion can stabilize
molten bituminous compositions having a polyethylene additive, those skilled in the
art would understand that other compositions having polymer additives of the same
type would be stabilized against gross phase separation by this stabilizer. In this
context, a polymer segment which is miscible with molten polyethylene so as to be
blended therein and anchored thereto and which forms stable droplets in the presence
of the stabilizer, as shown in Figure 2, thus is considered to be of the same type
as polyethylene. Polyethylene and poly(ethylene-co-vinyl acetate) are considered to
be polymers of the same type.
[0047] It has been found that an effective dispersion temperature is obtained at 10° to
50°C above the melting or fusion temperature of the polymer being dispersed, depending
on factors, such as polymer molecular weight, matrix viscosity and shear force of
mixing. Thus, a grade of polyethylene having a melting point of 100° to 135°C can
be dispersed at a temperature of from 100°C to 250°C. Commonly found low density,
linear low density and high density polyethylenes thus may be dispersed and stabilized
by a stabilizer of the present invention. Most polyethylenes used in consumer products
have fusion temperatures in the acceptable range and polyethylene blends, such as
are obtained as pelletized, flaked or powdered recycled material, are suitable for
dispersal in bitumens and may be stabilized according to the present invention.
[0048] An upper limit may be placed on the time and temperature used in dispersal of a polymer
in bitumen according to the disclosed embodiments of the present invention because
of the lack of stability of polybutadienes above about 210°C, especially in air. However,
it is possible to disperse a polymer in bitumen at a temperature higher than 210°C
if an inert gas, such as nitrogen, blankets the mixing process.
[0049] The quantity of steric stabilizer required to achieve the required stability is quite
small, generally less than about 2 wt% of bitumen, depending on several factors, such
as the dispersed amount of polymer and the microstructure of the steric stabilizer
formed, since different butadienes with different cis and trans-contents and vinyl
content may form different microstructures through different cross-linked extended
chains. Depending on the application to which the composition is put, the amount of
stabilizer may vary up to about 10 wt%. The cost of achieving the stability is economically
attractive.
[0050] While the use of the stabilized polyethylene-modified bitumen composition as a paving
material for all types of paving has been emphasized herein, the stabilized bitumen
composition also finds applications in preformed paving bricks, roofing membranes,
shingles, waterproofing membranes, sealants, caulks, potting resins and protective
finishes. Paving materials generally include aggregate, such as crushed stone pebbles,
sand etc., along with the bitumen composition. Similarly, other additives to the bitumen
composition are employed, depending on the end use to which the invention is put.
For example, a roofing material may be obtained by the addition of suitable fillers,
such as asbestos, carbonates, silicas, wood fibers, mica, sulfates, clays, pigments
and/or fire retardants, such as chlorinated waxes. For crack-filler applications,
an oxide may advantageously be added.
[0051] In the following Examples, samples of bitumen from two different sources were employed.
To the extent that the properties of these materials are known, they are summarized
in the following Table A:
TABLE A
Property |
Lloydminister 85 - 100 |
Bow River 290 |
Viscosity+, Pa s |
|
|
@ 100°C |
4.30 |
1.29 |
@ 120°C |
1.00 |
0.40 |
@ 140°C |
0.34 |
0.16 |
@ 160°C |
0.15 |
0.07 |
Density at 15°C, g mL-1 |
1.026 |
1.015 |
Molecular Weight*, g mol-1 |
1200 |
975 |
Composition§, % |
|
|
Asphaltenes |
10.8 |
10.3 |
Polar Aromatics |
28.0 |
25.5 |
Naphthene Aromatics |
43.1 |
45.6 |
Saturates |
18.1 |
18.5 |
+ Brookfield Viscometer |
* Ebulliometry |
§ ASTM D4124-86 |
EXAMPLES
Example 1 (comparative)
[0052] This Example illustrates conventional high shear mixing of polyethylene and bitumen.
[0053] In a one liter reactor, 100 parts of asphalt (Petro-Canada Bow River, Penetration
290 - see Table A above for properties) were heated to 150°C. Two parts of low density
polyethylene (Esso Chemicals LL-6101, Mn = 12,500 g mol
-1, Mw = 40,000 g mol
-1, Melt Index 20) then were added and dispersed in the asphalt as molten liquid droplets
with a high shear mixer (Brinkman Polytron Mixer) for 30 minutes at 150°C. After mixing
was stopped, the dispersion of polyethylene droplets rapidly coalesced and a viscous
polyethylene layer formed on the surface of the liquid asphalt, which could not be
readily redispersed. This lack of stability against gross phase separation, even after
high shear mixing, is typical of polyolefin dispersions in asphalt. The rapid coalescence
of the molten polyethylene particles is seen from the photograph of Figure 1.
Example 2 (comparative)
[0054] This Example illustrates the effect of added polyethylene wax to bitumen-polyethylene
emulsions.
[0055] In a one liter reactor, 100 parts of asphalt (Petro-Canada Bow River, Penetration
290) were heated to 150°C. Two parts of low density polyethylene (Esso Chemicals LL-6101)
and 0.5 parts of a carboxylated polyethylene wax (Eastman Chemicals Epolene C-16,
molecular weight = 8000 g mol
-1, density at 25°C = 0.908 g mol
-1, acid number = 5) then were added and dispersed as molten liquid droplets with a
high shear mixer as in Example 1. A fine dispersion of polyethylene droplets was obtained
in 15 minutes due to the presence of the C-16 wax but, after mixing was stopped, the
dispersion quickly separated into readily observable phases, a viscous polyethylene
surface layer being visible after the sample stood for a few hours. Although the carboxylated
polyethylene wax appears to hasten dispersal of the polyethylene within the asphalt,
this material apparently does not stabilize the dispersion against gross phase separation
once mixing is stopped.
Example 3
[0056] This Example illustrates the present invention.
[0057] Carboxylated polyethylene (0.5 parts Du Pont Fusabond D-101, density at 25°C = 0.920
g mol
-1, Melt Flow Index = 11 to 18; anhydride content = 0.07 g mole/kg of resin, base polymer
is linear low density polyethylene) was dispersed in 25 parts asphalt (Petro-Canada
Bow River, Penetration 290) at 150°C for 30 min. Then 1.4 parts liquid polybutadiene
(Ricon 134, Colorado Chemical Specialties Inc, Microstructure 80 ± 5% trans- and cis-
1,4, 20 ± 5% 1,2-vinyl, molecular weight (Mw) = 12,000, Acid Number (KOH/g) = nil),
0.6 parts of a liquid amine-terminated poly(butadiene-co-acrylonitrile) (ATBN) (10
per cent acrylonitrile, in liquid form, catalog No. 549, Scientific Polymer Products
Inc., amine equivalent weight = 1200 g/mole), and 0.2 parts elemental sulphur were
added in order and mixed under high shear for 2 hours at a temperature between 150°
and 170°C. To this stirred mixture was added 75 parts additional asphalt (Bow River
290) and 3 parts low density polyethylene (Esso Chemicals 6101, Melt Flow Index 20).
After 5 to 20 minutes dispersal of the polyethylene as liquid droplets was complete
and, after stirring was terminated, no visual changes in particle size and distribution
of polyethylene dispersion were apparent after 3 days storage at 160°C. The retained
dispersed nature of the polyethylene droplets can be seen from the photograph of Figure
2.
Example 4
[0058] The method of Example 3 was repeated with 3 parts of high density polyethylene (Du
Pont Sclair 2914, Melt Flow Index = 45, density at 25°C = 0.96 g mol
-1) instead of 3 parts of the low density polyethylene. The resulting asphalt emulsion
was stable for 3 days at 160°C without observable changes in particle size or viscosity.
Example 5
[0059] The method of Example 3 was repeated using 0.5 parts carboxylated polyethylene wax
(Eastman Chemical Products Epolene C-16 Wax, molecular weight less than 10,000), instead
of Du Pont Fusabond D-101 carboxylated polymer. This substitution also produced a
stable emulsion at 160°C. This experiment demonstrates that the carboxylated polyethylene
component may have a relatively low molecular weight (a wax having a molecular weight
less than 10,000 g/mole) as in this Example or a high molecular weight polymer (Melt
Flow Index 11-18) as in Example 3.
Example 6
[0060] The method of Example 3 was repeated with Lloydminster 85-100 Penetration grade asphalt
(Petro-Canada Clarkson Refinery - see Table A above for properties) instead of Bow
River 290 asphalt. The resulting emulsion was stable at 160°C.
Examples 7 to 9
[0061] The method of Example 3 was repeated with variable ratios of reactants as shown in
Table 1 below (parts by weight). The compositions of Examples 7 to 9 were all found
to be stable at 160°C for at least 3 days. These Examples demonstrate that the viscosities
and particle sizes of the emulsified particles may be adjusted by appropriate control
of the reagent concentrations.
Example 10 (comparative)
[0062] The method of Example 3 was repeated without the addition of 0.6 part amine terminated
(poly(butadiene-co-acrylonitrile)). The resulting emulsion underwent gross phase separation
as evidenced by microscopic observation.
Example 11 (comparative)
[0063] The method of Example 3 was repeated without the addition of sulphur. The resulting
emulsion was unstable against gross phase separation as evidenced by microscopic observation.
Example 12 (comparative)
[0064] The method of Example 3 was repeated without the addition of the liquid polybutadiene.
The resulting emulsion was unstable against gross phase separation, as evidenced by
microscopic observation.
Example 13
[0065] The method of Example 3 was repeated and the sample was permitted to cool to ambient
temperature, then reheated up to 160°C again several times. The stability of the polyethylene
dispersion in the asphalt and the viscosity of the sample were not obviously changed.
The reheated dispersed nature of the polyethylene droplets can be seen from the photograph
of Figure 3.
[0066] The results of the foregoing Examples 1 to 13 have been tabulated for convenience
of reference in the following Table I:
[0067] It should also be understood that the photographs of Figures 1 and 2 are of molten
bitumen-polymer compositions at an elevated temperature. The coalesced state shown
in Figure 1 illustrates a system which undergoes gross phase separation. Such a system
thus displays different behavior, over time, than the type of system shown in Figure
2. The Figure 1 system when dispersed, initially gives an appearance similar to that
shown in Figure 2, but with time the particles, whose movement is visible under a
hot-stage microscope at 160°C, coalesce into the large polymer particles shown in
Figure 1 as polymer droplets encounter each other. On the other hand, the system of
Figure 2, although the some movement of particles is evident, does not indicate any
coalescence of smaller particles into larger ones such as those of Figure 1. On a
larger scale, the system of Figure 1 undergoes readily observable gross phase separation
while the system of Figure 2 is stabilized against such gross phase separation. It
will further be appreciated that the diameters of stabilized particles evident in
Figure 2 are on the order of from about 0.1 to about 1 or 3 microns.
[0068] In summary, the present invention provides a stabilized polymer-modified bitumen
composition which resists polymer phase separation in liquid bitumen medium, both
at ambient and elevated temperatures, by the use of a unique steric stabilization
system. Modifications are possible within the scope of this invention.
1. A stable bitumen composition, comprising:
a continuous bitumen phase;
a particulate phase of an insoluble olefinic polymer dispersed in said bitumen phase;
and
a steric stabilizer of (a) a first component comprising a polydiene, soluble in said
bitumen, and (b) a second component comprising an olefinic polymer, the same as or
different from the olefinic polymer of the particulate phase, miscible with said particulate
phase so as to be anchored thereto, and chemically bonded to said first component
to maintain dispersed particles of said particulate phase spaced from each other in
said bitumen phase, so as to inhibit separation of said particulate phase from said
bitumen phase by progressive coalescence of the dispersed particles.
2. A composition as claimed in claim 1, wherein said bitumen phase comprises an asphalt
and said particulate phase comprises a homopolymer and/or copolymer of ethylene.
3. A composition as claimed in claim 1 or claim 2, wherein said second component is chemically
bonded to said first component by interaction of functional groups provided on the
respective components.
4. A composition as claimed in claim 3, wherein the olefinic polymer of the second component
is a carboxylated polyethylene and the polydiene of the first component is an amine-terminated
diene.
5. A composition as claimed in any one of claims 1 to 4, wherein said dispersed particulate
phase comprises 0.1 to 20 wt% of the continuous bitumen phase.
6. A composition claimed in any one of claims 1 to 5, wherein said first component comprises
0.1 to 3 wt% of the continuous bitumen phase and said second component comprises 0.1
to 5 wt% of the continuous bitumen phase.
7. A composition for forming a stable dispersion of a particulate phase of insoluble
olefinic polymer in bitumen, comprising:
bitumen; and
a pro-steric stabilizer of a bitumen-soluble polydiene chemically-bonded with a particulate
phase-compatible olefinic polymer which is the same as or different from the olefinic
polymer of the particulate phase and which is miscible with the olefinic polymer of
the particulate phase so as to be anchored thereto.
8. A composition as claimed in claim 7, wherein the particulate phase-compatible olefinic
polymer is a homopolymer and/or a copolymer of ethylene.
9. A method of forming a stable bitumen composition, comprising:
(a) forming, in a continuous bitumen phase, a particulate phase of an insoluble olefinic
polymer dispersed in said bitumen phase by dispersing the olefinic polymer in the
bitumen phase, at an elevated temperature above the fusion temperature of the olefinic
polymer, in the presence of a first component comprising a functionalized polydiene
soluble in said bitumen and a second component comprising a functionalized olefinic
polymer, the same as or different from the olefinic polymer of the particulate phase
and miscible with the particulate phase for anchoring thereto; and
(b) effecting chemical bonding between the first and second components by interaction
of the functional groups therein to form a steric stabilizer anchored to the particulate
phase and soluble in the bitumen phase, to maintain dispersed particles of said particulate
phase spaced from each other in said bitumen phase, so as to inhibit separation of
said particulate phase from said bitumen phase by progressive coalescence of the dispersed
particles.
10. A method as claimed in claim 9, wherein the olefinic polymer of the particulate phase
is a homopolymer and/or copolymer of ethylene having a fusion temperature which permits
dispersion of the olefinic polymer as molten droplets in the bitumen at a temperature
of 100 to 250°C.
11. A method as claimed in claim 10, wherein the homopolymer and/or copolymer of ethylene
comprises polyethylene having a melting point of from 100 to 135°C.
12. A method as claimed in any one of claims 9 to 11, wherein the functionalized polydiene
is a homopolymer or copolymer of an amine-terminated butadiene and the functionalized
olefinic polymer is a homopolymer or copolymer of a carboxylated ethylene.
13. A method as claimed in any one of claims 9 to 12, wherein additional bitumen is also
added to the bitumen composition.
14. A method of forming a bitumen composition, comprising:
dissolving a functionalized polydiene in bitumen; dispersing a functionalized olefinic
polymer in the bitumen; and
reacting the functionalized olefinic polymer and the functionalized polydiene so as
to bind the olefinic polymer to the polydiene, thereby to form in the bitumen a pro-steric
stabilizer for, in use,
maintaining a dispersed particulate phase of an olefinic polymer, the same as or
different from the olefinic polymer of the pro-steric stabiliser, to be added to the
composition.
15. A method as claimed in claim 14, wherein the functionalized polydiene is an amine-terminated
polybutadiene and the functionalized olefinic polymer is a carboxylated olefinic polymer.
16. A method claimed in claim 15, further comprising dissolving unfunctionalized polybutadiene
in the bitumen and subjecting the unfunctionalized polybutadiene to partial cross-linking
with the functionalized polybutadiene and itself.
17. A method as claimed in claim 16, wherein said unfunctionalised polybutadiene has a
molecular weight of from 500 to 45,000 and is soluble in or compatible with bitumen
at a mixing temperature of 150° to 200°C.
18. A method as claimed in claim 16 or claim 17, wherein the partial cross-linking is
initiated by a free-radical initiator.
19. A method as claimed in claim 18, wherein the free-radical initiator is sulphur, with
or without sulphur accelerators.
20. A method as claimed in claim 19, wherein carboxylated polyethylene, liquid unfunctionalized
polybutadiene, amine-terminated polybutadiene and elemental sulphur are dispersed
in bitumen at a temperature of 100° to 250°C by mixing for 0.1 to 3.5 hours until
a homogenous composition is formed.
21. A method as claimed in any one of claims 14 to 20, further comprising dispersing an
olefinic polymer in the bituminous composition to form a stable composition in which
the olefinic polymer component of the steric stabilizer is anchored to the olefinic
polymer particles dispersed in the bitumen to maintain the dispersed olefinic polymer
particles spaced from each other in the bitumen, so as to inhibit separation of the
particulate phase from the bitumen by progressive coalescence of dispersed particles.
1. Stabile Bitumen-Zusammensetzung, umfassend:
eine kontinuierliche Bitumenphase;
eine Teilchenphase eines unlöslichen olefinischen Polymeres, das in dieser Bitumenphase
dispergiert ist; und
einen sterischen Stabilisator aus (a) einer ersten Komponente, welche ein in diesem
Bitumen lösliches Polydien umfaßt und (b) eine zweite Komponente, welche ein olefinisches
Polymer, gleich oder verschieden von dem olefinischen Polymer der Teilchenphase, umfaßt,
das mit der Teilchenphase mischbar ist, um daran verankert und chemisch mit der ersten
Komponente verbunden zu werden, um dispergierte Teilchen dieser Teilchenphase in der
Bitumenphase beabstandet voneinander zu halten, um eine Abscheidung der Teilchenphase
von der Bitumenphase durch fortschreitende Koaleszenz der dispergierten Teilchen zu
verhindern.
2. Zusammensetzung nach Anspruch 1, worin die Bitumenphase einen Asphalt umfaßt und die
Teilchenphase ein Homopolymer und/oder Copolymer von Ethylen umfaßt.
3. Zusammensetzung nach Anspruch 1 oder 2, worin die zweite Komponente chemisch mit der
ersten Komponente durch Wechselwirkung funktioneller Gruppen verbunden ist, welche
an den jeweiligen Komponenten vorgesehen sind.
4. Zusammensetzung nach Anspruch 3, worin das olefinische Polymer der zweiten Komponente
ein carboxiliertes Polyethylen ist und das Polydien der ersten Komponente ein Dien
mit endständiger Amingruppe ist.
5. Zusammensetzung nach einem der Ansprüche 1 bis 4, worin die dispergierte Teilchenphase
0,1 bis 20 Gew% der kontinuierlichen Bitumenphase umfaßt.
6. Zusammensetzung nach einem der Ansprüche 1 bis 5, worin die erste Komponente 0,1 bis
3 Gew% der kontinuierlichen Bitumenphase und die zweite Komponente 0,1 bis 5 Gew%
der kontinuierlichen Bitumenphase umfaßt.
7. Zusammensetzung zur Erzeugung einer stabilen Dispersion einer Teilchenphase eines
unlöslichen olefinischen Polymeres in Bitumen, umfassend:
Bitumen; und
einen pro-sterischen Stabilisator eines in Bitumen löslichen Polydienes, das chemisch
mit einem mit der Teilchenphase kompatiblen olefinischen Polymer verbunden ist, das
gleich oder verschieden von dem olefinischen Polymer der Teilchenphase ist und das
mit dem olefinischen Polymer der Teilchenphase mischbar ist, um daran verankert zu
werden.
8. Zusammensetzung nach Anspruch 7, worin das mit der Teilchenphase kompatible olefinische
Polymer ein Homopolymer und/oder ein Copolymer von Ethylen ist.
9. Verfahren zur Bildung einer stabilen Bitumenzusammensetzung, umfassend:
(a) Erzeugen, in einer kontinuierlichen Bitumenphase, einer Teilchenphase eines unlöslichen
olefinischen Polymeres, das in der Bitumenphase durch Dispergieren des olefinischen
Polymeres in der Bitumenphase bei einer über die Schmelztemperatur des olefinischen
Polymeres erhöhten Temperatur in Gegenwart einer ersten Komponente dispergiert wird,
welche ein funktionalisiertes Polydien umfaßt, das in dem Bitumen löslich ist und
einer zweiten Komponente, welche ein funktionalisiertes olefinisches Polymer umfaßt,
das gleich oder verschieden von dem olefinischen Polymer der Teilchenphase ist und
mischbar mit der Teilchenphase zur Verankerung daran ist; und
(b) Bewirken einer chemischen Bindung zwischen den ersten und zweiten Komponenten
durch Wechselwirkung der funktionellen Gruppen darin, um einen sterischen Stabilisator
zu erzeugen, welcher mit der Teilchenphase verankert und in der Bitumenphase löslich
ist, um dispergierte Teilchen der Teilchenphase beabstandet voneinander in der Bitumenphase
zu halten, um eine Abscheidung der Teilchenphase aus der Bitumenphase durch fortschreitende
Koaleszenz der dispergierten Teilchen zu verhindern.
10. Verfahren nach Anspruch 9, worin das olefinische Polymer der Teilchenphase ein Homopolymer
und/oder Copolymer von Ethylen mit einer Schmelztemperatur ist, welche eine Dispersion
des olefinischen Polymeres in Form geschmolzener Tropfen in dem Bitumen bei einer
Temperatur von 100 bis 250°C ermöglicht.
11. Verfahren nach Anspruch 10, worin das Homopolymer und/oder Copolymer von Polyethylen
mit einem Schmelzpunkt von 100 bis 135°C umfaßt.
12. Verfahren nach einem der Ansprüche 9 bis 11, worin das funktionalisierte Polydien
ein Homopolymer oder Copolymer eines Butadienes mit endständiger Amingruppe und das
funktionalisierte olefinische Polymer ein Homopolymer oder Copolymer eines carboxylierten
Ethylens ist.
13. Verfahren nach einem der Ansprüche 9 bis 12, worin zusätzliches Bitumen der Bitumenzusammensetzung
zugegeben wird.
14. Verfahren zur Erzeugung einer Bitumenzusammensetzung, umfassend:
Auflösen eines funktionalisierten Polydiens in Bitumen; Dispergieren eines funktionalisierten
olefinischen Polymeres in dem Bitumen; und
Umsetzen des funktionalisierten olefinischen Polymeres und des funktionalisierten
Polydienes, um das olefinische Polymer mit dem Polydien zu verbinden, um dadurch in
dem Bitumen einen pro-sterischen Stabilisator zu erzeugen, um bei der Verwendung eine
dispergierte Teilchenphase eines olefinischen Polymeres, das gleich oder verschieden
von dem olefinischen Polymer des pro-sterischen Stabilisators ist, welcher der Zusammensetzung
zuzugeben ist, aufrechtzuerhalten.
15. Verfahren nach Anspruch 14, worin das funktionalisierte Polydien ein Polybutadien
mit endständigen Amingruppen und das funktionalisierte olefinische Polymer ein carboxiliertes
olefinisches Polymer ist.
16. Verfahren nach Anspruch 15, das des weiteren ein Auflösen von nicht-funktionalisiertem
Polybutadien in dem Bitumen und ein Unterwerfen des nicht-funktionalisierten Polybutadiens
einer teilweisen Vernetzung mit dem funktionalisierten Polybutadien und sich selbst
umfaßt.
17. Verfahren nach Anspruch 16, worin das nichtfunktionalisierte Polybutadien ein Molekulargewicht
von 500 bis 45.000 aufweist und bei einer Temperatur von 100°C bis 200°C in Bitumen
löslich oder damit kompatibel ist.
18. Verfahren nach Anspruch 16 oder 17, worin die teilweise Vernetzung durch einen Radikalstarter
eingeleitet wird.
19. Verfahren nach Anspruch 18, worin der Radikalstarter Schwefel mit oder ohne Schwefelbeschleuniger
ist.
20. Verfahren nach Anspruch 19, worin carboxiliertes Polyethylen, flüssiges nicht-funktionalisiertes
Polybutadien, Polybutadien mit endständiger Amingruppe und elementarer Schwefel in
Bitumen bei einer Temperatur von 100 bis 250°C durch Vermischen während 0,1 bis 3,5
Stunden dispergiert werden, bis eine homogene Zusammensetzung gebildet ist.
21. Verfahren nach einem der Ansprüche 14 bis 20, das des weiteren ein Dispergieren eines
olefinischen Polymeres in der bituminösen Zusammensetzung umfaßt, um eine stabile
Zusammensetzung zu erzeugen, in welcher die olefinische Polymerkomponente des sterischen
Stabilisators mit dem olefinischen Polymerteilchen, welche in dem Bitumen dispergiert
sind, verankert werden, um die dispergierten olefinischen Polymerteilchen voneinander
in dem Bitumen beabstandet zu halten, um die Abscheidung der Teilchenphase aus dem
Bitumen durch fortschreitende Koaleszenz der dispergierten Teilchen zu verhindern.
1. Composition de bitume stable comprenant:
une phase de bitume continue ;
une phase particulaire d'un polymère oléfinique insoluble dispersée dans ladite phase
de bitume ; et
un stabilisant stérique de (a) un premier composant comprenant un polydiène, soluble
dans ledit bitume, et (b) un second composant comprenant un polymère oléfinique, identique
ou différent du polymère oléfinique de la phase particulaire; miscible avec ladite
phase particulaire de manière à être ancré à celle-ci, et lié chimiquement audit premier
composant pour maintenir les particules dispersées de ladite phase particulaire distantes
les unes des autres dans ladite phase de bitume, de manière à inhiber la séparation
de ladite phase particulaire d'avec ladite phase de bitume par coalescence progressive
des particules dispersées.
2. Composition selon la revendication 1, dans laquelle ladite phase de bitume comprend
un asphalte et ladite phase particulaire comprend un homopolymère et/ou un copolymère
de l'éthylène.
3. Composition selon la revendication 1 ou la revendication 2, dans laquelle ledit second
composant est lié chimiquement audit premier composant par interaction de groupes
fonctionnels présents sur les composants respectifs.
4. Composition selon la revendication 3, dans laquelle le polymère oléfinique du second
composant est un polyéthylène carboxylé et le polydiène du premier composant est un
diène amino-terminé.
5. Composition selon l'une quelconque des revendications 1 à 4, dans laquelle ladite
phase particulaire dispersée constitue 0,1 à 20 % en masse de la phase de bitume continue.
6. Composition selon l'une quelconque des revendications 1 à 5, dans laquelle ledit premier
composant constitue 0,1 à 3 % en masse de la phase de bitume continue et ledit second
composant constitue 0,1 à 5 % en masse de la phase de bitume continue.
7. Composition pour former une dispersion stable d'une phase particulaire d'un polymère
oléfinique insoluble dans du bitume comprenant:
du bitume et
un stabilisant pro-stérique d'un polydiène soluble dans le bitume lié chimiquement
à un polymère oléfinique compatible avec la phase particulaire qui est identique ou
différent du polymère oléfinique de la phase particulaire et qui est miscible avec
le polymère oléfinique de la phase particulaire de manière à être ancré à celle-ci.
8. Composition selon la revendication 7, dans laquelle le polymère oléfinique compatible
avec la phase particulaire est un homopolymère et/ou un copolymère de l'éthylène.
9. Procédé de formation d'une composition de bitume stable comprenant
(a) la formation, dans une phase de bitume continue, d'une phase particulaire d'un
polymère oléfinique insoluble dispersé dans ladite phase de bitume par dispersion
du polymère oléfinique dans la phase de bitume, à une température élevée supérieure
à la température de fusion du polymère oléfinique, en présence d'un premier composant
comprenant un polydiène fonctionnalisé soluble dans ledit bitume et un second composant
comprenant un polymère oléfinique fonctionnalisé, identique ou différent du polymère
oléfinique de la phase particulaire et miscible avec la phase particulaire pour l'ancrage
à celle-ci ; et
(b) la formation d'une liaison chimique entre les premier et second composants par
interaction de leurs groupes fonctionnels pour former un stabilisant stérique ancré
à la phase particulaire et soluble dans la phase de bitume, pour maintenir les particules
dispersées de ladite phase particulaire distantes les unes des autres dans ladite
phase de bitume, de manière à inhiber la séparation de ladite phase particulaire d'avec
ladite phase de bitume par coalescence progressive des particules dispersées.
10. Procédé selon la revendication 9, dans lequel le polymère oléfinique de la phase particulaire
est un homopolymère et/ou un copolymère de l'éthylène ayant une température de fusion
qui permet la dispersion du polymère oléfinique sous forme de gouttelettes fondues
dans le bitume à une température de 100 à 250°C.
11. Procédé selon la revendication 10, dans lequel l'homopolymère et/ou le copolymère
de l'éthylène comprend un polyéthylène ayant un point de fusion de 100 à 135°C.
12. Procédé selon l'une quelconque des revendications 9 à 11, dans lequel le polydiène
fonctionnalisé est un homopolymère ou copolymère d'un butadiène amino-terminé et le
polymère oléfinique fonctionnalisé est un homopolymère ou copolymère d'un éthylène
carboxylé.
13. Procédé selon l'une quelconque des revendications 9 à 12, dans lequel du bitume supplémentaire
est ajouté aussi à la composition de bitume.
14. Procédé de formation d'une composition de bitume comprenant :
la dissolution d'un polydiène fonctionnalisé dans du bitume;
la dispersion d'un polymère oléfinique fonctionnalisé dans le bitume; et
la réaction du polymère oléfinique fonctionnalisé et du polydiène fonctionnalisé de
manière à lier le polymère oléfinique au polydiène, pour former ainsi dans le bitume
un stabilisant pro-stérique pour maintenir pendant l'utilisation une phase particulaire
dispersée d'un polymère oléfinique, identique ou différent du polymère oléfinique
du stabilisant pro-stérique, à ajouter à la composition.
15. Procédé selon la revendication 14, dans lequel le polydiène fonctionnalisé est un
polybutadiène amino-terminé et le polymère oléfinique fonctionnalisé est un polymère
oléfinique carboxylé
16. Procédé selon la revendication 15, comprenant en outre la dissolution d'un polybutadiène
non fonctionnalisé dans le bitume et la soumission du polybutadiène non fonctionnalisé
à une réticulation partielle avec le polybutadiène fonctionnalisé et avec lui-même.
17. Procédé selon la revendication 16, dans lequel ledit polybutadiène non fonctionnalisé
a une masse moléculaire de 500 à 45 000 et est soluble dans ou compatible avec le
bitume à une température de mélange de 150° à 200°C.
18. Procédé selon la revendication 16 ou la revendication 17, dans lequel la réticulation
partielle est initiée par un initiateur radicalaire.
19. Procédé selon la revendication 18, dans lequel l'initiateur radicalaire est le soufre
avec ou sans accélérateurs pour le soufre.
20. Procédé selon la revendication 19, dans lequel du polyéthylène carboxylé, du polybutadiène
non fonctionnalisé liquide, du polybutadiène amino-terminé et du soufre élémentaire
sont dispersés dans le bitume à une température de 100° à 250°C par mélange pendant
0,1 à 3,5 h jusqu'à ce qu'une composition homogène soit formée.
21. Procédé selon l'une quelconque des revendications 14 à 20, comprenant en outre la
dispersion d'un polymère oléfinique dans la composition bitumineuse pour former une
composition stable dans laquelle le composant polymère oléfinique du stabilisant stérique
est ancré aux particules de polymère oléfinique dispersées dans le bitume pour maintenir
les particules de polymère oléfinique dispersées distantes les unes des autres dans
le bitume, de manière à inhiber la séparation de la phase particulaire d'avec le bitume
par coalescence progressive des particules dispersées.